Viewpoints: Is there a right way to kill an animal?

Supporters of moves to end the slaughter of unstunned animals say methods employed by Jews and Muslims for centuries are inhumane. Others say the nature of religious slaughter is misunderstood. Here two scientists present opposing cases.

Dr Stuart Rosen, Faculty of Medicine, Imperial College, London

Jewish law (halacha) ensures that all aspects of an animal's welfare are protected, not merely the last moment of its life.

The whole point of shechita - the only method of slaughter by which Jews are permitted to eat kosher meat and poultry - is to be fast and humane.

The shochet, who performs shechita, undergoes years of training. A perfectly clean and swift incision with a surgically sharp instrument (chalef) severs the structures at the front of the neck - the trachea, oesophagus, carotid arteries and jugular veins.

There is ample scientific evidence that shechita is at least as humane as conventional slaughter

The speed and precision of the incision ensures the lack of stimulation of the severed structures and results in the immediate loss of consciousness. Blood flow to the brain is completely halted.

In addition, blood empties rapidly from the brain. Irreversible cessation of consciousness and insensibility to pain are achieved, providing the most effective stun. There is no delay between the shechita stun and subsequent death so the animal cannot regain consciousness, as can happen with conventional slaughter methods.

Conventional methods of stunning in the UK by use of a captive bolt, gassing or electrocution (by electrified pincers for larger animals or a water bath with an electric current running through it for poultry) paralyse the animal and it is unable to display outward signs of feeling pain.

However, it is quite impossible to know whether the conventionally stunned animal is feeling pain or not. We do know, though, that millions of animals each year are mis-stunned through faulty stunning equipment, or its misapplication to the animal.

There is ample scientific evidence that shechita is at least as humane as conventional slaughter. Research in London and America, including by Dr Temple Grandin - one of the pre-eminent authorities in animal welfare - have supported this view.

In contrast, many of the studies which have suggested that shechita causes unnecessary pain have been agenda-driven and methodologically flawed, stretching data in a distinctly unscientific fashion to unsupported conclusions.

It is unfortunate that some animal welfare organisations in the UK and elsewhere tend to view religious slaughter as incompatible with the principles of humaneness and animal welfare. Quite the contrary is true - compassion and animal welfare stand at the centre of the entire shechita process.

Dr Stuart Rosen (MA, MD, FRCP) is the author of Physiological Insights into Shechita, published in The Veterinary Record (June 12, 2004 Vol. 154)

Dr James Kirkwood, The Humane Slaughter Association

Around the world, traditions about our interactions with animals (farmed, pets, wild and others) are being re-evaluated in the light of developing scientific understanding of their biology and needs.

It is now widely believed that other vertebrate animals (and perhaps some invertebrates) have, like us, the capacity to subjectively feel - to be aware of - painful stimuli and that this capacity evolved because of the protective advantages it confers.

If animals are slaughtered without stunning they may, before losing consciousness, feel pain and other unpleasant feelings

Efforts are increasingly being made, therefore, to avoid unnecessarily causing pain or other unpleasant feelings to animals. For example, there have been great advances in veterinary anaesthesia and analgesia that enable the amelioration of pain in animals associated with surgical treatments or due to injury or disease.

Likewise, methods have been researched and developed during the last century to stun food animals - to make them unconscious so as to preclude the possibility of pain or other unpleasant feelings - prior to the cutting of major blood vessels to cause death by blood loss.

The need for this has been further confirmed by the results of recent research in New Zealand which shows that neck cuts in lightly anaesthetised cattle cause pain receptors to send signals resulting in brain activity that in a conscious animal would be perceived as pain, and that this can be prevented by stunning.

If animals are slaughtered without stunning they may, before losing consciousness, feel pain and other unpleasant feelings associated with the cutting of neck tissues to sever the major blood vessels.

A review by Karen von Holleben and others (2010) of studies relevant to assessment of time to loss of consciousness following a ventral neck cut concluded "most of the cattle seem to lose consciousness between five and 90 seconds after the cut", and "sheep seem to lose consciousness within two to 20 seconds after ventral neck cut". Time to loss of consciousness had been found to average 12-15 seconds in a recent study in poultry.

As stated in this review: "In summary, part of the welfare concerns about performing a ventral neck cut on an unstunned animal arises, because following the cut it may take some time to achieve unconsciousness."

Modern stunning methods are a major advance in pursuit of the humane ideal (that also lies behind various ancient traditional slaughter methods) of avoidance or minimising the risk of causing pain or other unpleasant feelings at the time of slaughter.

Dr James Kirkwood (BVSc PhD FBS MRCVS) is a veterinarian and chief executive and scientific director of the Universities Federation for Animal Welfare.